1. Field of the Invention
The present invention relates to an improved pneumatically operated device for collecting live biological specimens beneath the surface of a body of water.
2. Description of the Prior Art
There are many instances in which live, biological specimens are required to enhance the knowledge available concerning fish and other marine and aquatic creatures. While some specimens may be captured live with baited traps lowered into a body of water and left for later collection, this collection method is often unsatisfactory. Such unattended traps are not specific to any particular species of marine or aquatic life so that an ichthyologist has very little control over the particular species, if any, which will be attracted to the traps. Furthermore, it is often difficult to determine locations under water which are frequented by a species of interest. It is therefore difficult to place an unattended trap so that specimen collection is likely to be successful.
Live specimen collection is more effectively conducted by a diver who actually enters a body of water and personally selects and collects a specimen of interest. Virtually all diving of this type which requires underwater observation for extended periods is performed with self-contained life supporting tanks, masks, and wet suits, commonly referred to as scuba equipment.
One of the simplest specimen collection aids to a diver is a net, the edges of which are held apart by a circular hoop which is mounted on an elongated handle. The diver can attempt to scoop a specimen up in a net, manually close off the mouth of the net to prevent a specimen from escaping, and attempt to transfer the live specimen to a collection container. However, collection attempts using a net are frequently unsuccessful.
Another device which was developed for the purpose of collecting live biological specimens is an implement known as a "slurp gun". The description of one embodiment of a slurp gun appears in an article entitled "a pneumatically operated slurp gun", authored by J. Ross Wilcox, Robert P. Meek and David Mook which appeared in the publication Limnology and Oceanography, Vol. 19, No. 2, March 1974, pages 354-355.
A slurp gun operates on the same principle as a syringe. That is, a plunger is retracted within a cylindrical tube under water to rapidly draw a volume of water into a receiving chamber through an intake. A nozzle at the intake or mouth of the receiving chamber is positioned as closely as possible to a live biological specimen of interest, and the plunger is retracted within the tube under the control of a pneumatic cylinder. A pneumatic cylinder is coupled to operate the plunger and is pneumatically connected to a conventional scuba tank containing compressed air through a three way control valve.
In a first position the control valve allows a compressed volume of air to return the plunger to a position proximate to the receiving chamber intake. A trigger mechanism on the control valve is employed to move the valve to a second position in which compressed air under a significantly greater pressure is introduced into the opposite chamber of the pneumatic cylinder. The plunger is thereupon retracted within the tube to suck in a volume of water through the intake. If a live biological specimen of interest is located close enough to the nozzle, it will be carried into the receiving chamber through the intake upon actuation of the plunger.
In a third position the control valve allows air to be bled from the highly pressurized chamber of the pneumatic cylinder. When pressure drops below the pressure in the opposing chamber, the pressure in the opposing chamber operates against the pneumatic piston, which in turn returns the plunger to a position proximate to the receiving chamber intake in preparation for a subsequent specimen collection attempt.
While some success in live biological specimen collection has been achieved with slurp guns of a conventional design, such as that described, several distinct problems exist in the use of such devices. It is frequently very difficult to position the nozzle of a conventional slurp gun close enough to a biological specimen of interest for a sufficient suction force to be exerted to draw the specimen into a receiving chamber. The approach of the nozzle will often cause the creature of interest to swim away. As a result, the suctional force exerted on the specimen is inadequate or misdirected, and the creature is not drawn into the slurp gun at all. On other occasions the live specimen is drawn only partially into the device, and is able to rapidly escape once the initial suction force has abated. A further deficiency of conventional slurp guns exists in that the inlet remains open at all times, and the entrapped specimen is likely to escape through it even if the slurp gun has been successfully operated to effectuate an initial capture.